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Synlett 2011(2): 223-226  
DOI: 10.1055/s-0030-1259304
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Modular ‘Click’ Approach to Substituted 2,2′-Bipyridines

Pierangelo Fabbrizzi, Bianca Cecconi, Stefano Cicchi*
Dipartimento di Chimica ‘Ugo Schiff’, Università degli Studi di Firenze, Via della Lastruccia 3-13, 50019 Sesto Fiorentino, Firenze, Italy
Fax: +39(055)4573531; e-Mail: stefano.cicchi@unifi.it;
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Publication History

Received 11 October 2010
Publication Date:
05 January 2011 (online)

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Abstract

The CuAAC reaction was used for the development of a click approach to a series of triazole-substituted bipyridinyl derivatives. 4,4′-Diethinyl 2,2′-bipyridine and 4,4′-diazido 2,2′-bipyridine were synthesized and tested in the cycloaddition reactions. While 4,4′-diazido 2,2′-bipyridine revealed unreactive in CuAAC reactions, its corresponding N,N′-dioxide afforded the expected cycloaddition product.

Key words

cycloaddition - azides - alkynes - copper - ligands

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4,4′-Bis{1-benzyl-1 H -[1,2,3]triazol-4-yl}-[2,2′]bipyridinyl (3a)
¹H NMR (400 MHz, DMSO-d 6): δ = 9.00 (s, 2 H), 8.87 (dd, J = 0.8, 1.6 Hz, 2 H), 8.76 (dd, J = 0.8, 5.2 Hz, 2 H), 7.89 (dd, J = 1.6, 5.2, Hz, 2 H), 7.44-7.33 (m, 10 H), 5.70 (s, 4 H). ¹³C NMR (50 MHz, CDCl3): δ = 155.9, 149.5, 138.7, 133.8, 129, 128.7, 127.9, 121.1, 119.8, 117, 54.2. IR (KBr): 3112, 3000, 1607, 1400, 1207 cm-¹. MS (EI, 70 eV): m/z (%) = 470.2 (33.3) [M+], 236.7 (6.9), 60 (12.2), 43.8 (100), 32 (71.6). Anal. Calcd for C28H22N8: C, 71.47; H, 4.71; N, 23.81. Found C, 71.23; H, 4.85; N, 23.96.

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Caution: Azido derivatives are known as potentially explosive compounds. Although we encountered no problems in manipulating these products, it is important to protect the operator from any possible explosion hazard.
4,4′-Diazido[2,2′]bipyridinyl (2)
¹H NMR (300 MHz, CDCl3): δ = 8.58 (d, J = 5.3 Hz, 2 H), 8.15 (d, J = 2.3 Hz, 2 H), 6.96 (dd, J = 2.3, 5.3 Hz, 2 H). ¹³C NMR (75 MHz, CDCl3): δ = 157.3, 150.1, 134.1, 114.2, 111.1. IR (KBr): 2117, 1580, 1456, 1207 cm-¹. MS (EI, 70 eV): m/z (%) = 238 (49) [M+], 182 (66), 155 (22), 128 (53), 104 (34), 77 (49), 64 (46), 52 (100). Anal. Calcd for C10H6N8O2: C, 50.42; H, 2.54; N, 47.04. Found C, 50.76; H, 2.26, N, 46.68.

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4,4′-Diazido[2,2′]bipyridinyl 1,1′-Dioxide (15)
¹H NMR (200 MHz, CDCl3): δ = 8.28 (d, J = 7.2 Hz, 2 H), 7.43 (d, J = 3.2 Hz, 2 H), 7.01 (dd, J = 7.2, 3.2 Hz, 2 H). ¹³C NMR (50 MHz, DMSO-d 6): δ = 143.1, 140.5, 136.5, 119.6, 118.4. IR (KBr): 3025, 2122, 1461, 1430 cm-¹. ESI-MS: m/z (%) = 293.1 (31) [M + Na+], 271.1 (99) [M + H+], 245.1 (32), 229.1 (11). Anal. Calcd for C10H6N8O2: C, 44.45; H, 2.24; N, 41.47. Found: C, 44.12; H, 1.92; N, 41.54.

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4,4′-Bis{4-phenyl[1,2,3]triazol-1-yl}-[2,2′]bipyridinyl 1,1′-Dioxide (16)
¹H NMR (400 MHz, DMSO-d 6): δ = 9.44 (s, 2 H), 8.65 (d, J = 6.4 Hz, 2 H), 8.47 (s, 2 H), 8.19 (d, J = 6.4 Hz, 2 H), 7.91 (m, 4 H), 7.51 (m, 4 H), 7.40 (m, 2 H). ¹³C NMR (100 MHz, DMSO-d 6): δ = 148.2, 143.2, 141.1, 131.9, 130.2, 129.6, 129, 125.8, 120.1, 119.6, 118.28 IR (KBr): 3055, 1653, 1506 cm-¹. ESI-MS: m/z (%) = 475 (100) [M - H+], 419.3 (36), 376.1 (27), 347.2 (66), 319.3 (32), 284.4 (22), 233.2 (16). Anal. Calcd for C26H18N8O2: C, 65.82; H, 3.82; N, 23.62. Found C, 65.52; H, 3.93; N, 23.27.